This invention relates to piezoelectric polymeric films and, more particularly, concerns such films which function as a mobile microphone when strips or portions thereof are conformably secured to the surfaces of an inflated balloon, or the film itself is made to function as the inflated balloon. The electrodes disposed on the film are connected to a suitable receiving device for processing the electrical signal generated by the film.
Underwater acoustic transducers employing polymeric piezoelectric film materials are known. In British Pat. No. 2,120,902, a shell of PVDF material inflated with nitrogen is provided with the usual conductive coatings on each face thereof. When an alternating current of 100 cycles per second is applied to the coatings, the shell vibrates to act as an underwater sound generator. The British Patent also discloses that the device may be used as an underwater sound detector by processing electrical signals generated in the coatings on the PVDF shell.
In U.S. Pat. No. 2,939,970, a spherical microphone assembly includes spherical outer and inner electrodes with a spherical piezoelectric ceramic transducer element therebetween. The assembly may also be used as a loudspeaker.
In U.S. Pat. No. 4,284,921, various configurations, including hemispherical, of thermoformed piezoelectric polymeric film materials are disclosed as transducer elements for purposes of receiving and transmitting.
A need has developed for a microphone which is air buoyant, light in weight, maneuverable, and deflatable for easy storage and transport.